Off-peak water heating system



D. J. MCCARTHY Filed Oct. 18, 1940 OFF-PEAK WATER HEATING SYSTEM rr rf fr fr f/ INVENTOR EAN/2 J/VCARrY BY w77 ATTORNEY Dec. 16, 1941.

Patented Dec. 16, 1941 OFF-PEAK WATER HEATING SYSTEM Daniel J. McCarthy, Elgin, Ill., assigner to Mc- Graw Electric Company, Elgin, Ill., a corporation of Delaware Application October 18, 1940, Serial No. 361,661

11 Claims.

y My invention relates to hot water tanks and more particularly to ofi-peak water heating systems for use with such hot water tanks.

One of the objects of my invention is to provide a relatively simple off-peak Water heating system embodying a minimum number of control elements.

Another object of my invention is to provide an olf-peak Water heating system embodying means for ensuring starting of the heating of the water at the start of an off-peak period if the tank contains less than a given quantity of hot water and for delaying starting of the heating, after the start of an oil-peak period, in case the tank contains more than a predetermined amount of hot water at the start of an oli-peak period.

Another object of my invention is to provide an ofi-peak Water heating system which will continue heating of the water in the tank in case the tank is not full of hotv water at the end of an opeak period.

Other objects of my invention will either beY evident from a description of one system embodying my invention or will be pointed out in the course of such -description and will be more particularly pointed out in the appended claims.

In the single sheet of drawings,

Figure 1 is a view showing a hot water tank in vertical section, certain control elements mounted thereon and other parts of a system embodying my invention, and,

Fig. 2 is a fragmentary view of a part of a timing device constituting a part of my system.

I have illustrated a hot Water tank which is shown as of elongated cylindrical shape to indicate the ordinary hot water tank used in domestic heating. This tank includes a cold water inlet pipe |3 and a hot water outlet pipe l5. The tank may be surrounded with heat insulating material I1 which may be covered by an outer thin sheet metal casing I3, the whole assembly being supported by a plurality of legs 2|. It is to be understood that while I have illustrated a, specific form oi hot water tank, my invention is not limited thereto and the tank and closely associated parts are shown merely ior illustrative purposes.

I provide a continuously operative timing means 23 which includes an electric motor 25 having a worm gear 21 mounted on its shaft which Worm gear is adapted to mesh with and to cause rotation of a circular disc 23. This disc 23 is mounted on a shaft 3| and While I have not illustrated any bearings for this shaft, these are to be understood as being provided. I desire further to point out that while I have illustrated a continuously operative timing device generally only, I do not desire to be limited to the specic details shown since I may use similar forms of continuously operative timing devices now well known in the art. It is to be understood that the electric motor 25 is operative to cause one complete rotation of disc 23 and shaft 3| in a twenty-four hour day.

I provide a cam disc 33 mounted on the shaft 3| and the greater part of the periphery of disc 33 is of uniform outer radius. A predetermined portion of the peripheral extent of disc 33 is oi slightly larger diameter and this portion is designated by the numeral 35.

'I'he peripheral extent of portion 35 is that decided upon by the public service station or utility providing electric current as being the oil-peak period, during which they will provide electric current at rates less than those in effect during the rest of a twenty-four hour day. It will be noted that I have illustrated the peripheral extent of portion 35 as being substantially onethird of the total periphery, that is, it covers or corresponds to an eight-hour oli-peak period. For illustrative purposes it may be noted that the off-peak period may extend from 10:00 p. m. to 6:00 a. m. I do not desire to be limited to this particular length of off-peak period nor to the hour of starting and of ending thereof but, as hereinbefore noted, these are given by way oi example. It will be noted further that the tim-v ing device is shown in the position in which certain parts thereof will be located at the start of an off-peak period, say at 10:00 p. m.

The electric motor 25 is energized from a supply circuit including conductors 31 and 33.

I provide a mechanically actuated control switch 4| including a. relatively rigid contact arm 43 and a resilient contact arm 45 which is normally biased out of engagement with arm 43 but is moved into engagement therewith when a lug 41 on arm 45, which may be of electric-insulating material, is engaged with the outer surface of portion 35 of disc 33.

I provide a single electromagnetic contactar 49 which includes in addition to a coil 5|, an electromagnetic armature core 53, a pair of spaced fixed contact members 55 and a movable contact bridging member 5l, all in a manner now well known in the art of electric circuit control.

Supply circuit conductor 3l is connected through a conductor 5S with contact arm 45 and a conductor 5| connects conductor 53 with one of the iixed contact members 55. 'I'he other fixed contact member 55 is connected through a conductor 63 and a conductor 65 with one terminal of an electric heater 61 associated with the tank` The other terminal of the heater is connected to a substantially rigid contact arm 69 of a thermally actuable switch 1|. The switch 1| includes a second substantially resilient contact arm 13 and a tubular member 15 suitably secured to the wall of the tank to be positioned inside of the tank. Arm 13 is normally yieldingly biased into engagement with contact arm 69. The switch includes also an expansion rod 11 which is adapted to cause movement of contact arm 13 away from contact arm 69 when the tubular member 15 is surrounded by hot water or'by water having a. given temperature. While I have shown a particular form of thermally-actuable switch I do not desire to be limited thereto as any other form of thermally-actuable switch operative for the same purpose may be used.

Contact arm 13 of switch 1| is connected through a conductor 19 to the other supply circuit 39. Itrmay be here pointed out that when contact bridgingmember 51 is in engagement with the cooperating xed contact members 55 and in case tubular member 15 of the main thermally actuable switch 1| is surrounded by cold water, energization of the heating element 61 will be eiected by a circuit substantially as follows: From supply circuit conductor 31 through conductors 59 and 6|, contact members 55 and 51, conductors 63 and 65 to heater 51, through contact arms 69 and 13 of switch 1| and through conductor 19- to the other supply circuit conductor 39.

I provide further an auxiliary thermally actuable switch 8| comprising a tubular m'ember 83, a thermally expansiblejiod 85 therein, a relatively rigid contact arm'81 and a resilient contact arm 89 engaged by rod 85 and moved thereby into and out of engagement with contact arm 81, the two contact arms 81 and 89 being out of engagement as shown in Fig. 1 ofthe drawing when tubular member 83 is surrounded by hot water.

Contact arm 43 of switch 4| is connected by a conductor A9| to contact arm 89 while contact arm 81 is connected to conductor 65 and to one terminal of coil 5| by a conductor 93. The other terminal of coil 5| is connected through a conductor 95 to-contact arm 69 of main thermal switch 1 I.

Let it be assumed that with the parts hereinbefore described in thepositions shown in Fig. 1 of the drawing, that is, the contact arms of switch 4| have been moved, into engagement and the quantity of hot water in the tank is suiiicient to envelope the tube 83 with hot water, in which case contact arm.89 'is out of engagement with contact arm 81. In this case energization of the coily 5| will not occur at the start of an off-peak period since the energizing circuit for this coil is substantially as follows: From supply circuit conductor 31 through conductor 59, contact arms 45 and 43, conductor 9|, contact arms 89 and 81 (when in engagement with each other) conin the tank at the start of an o-peak period is so small that tubular member 83 is surrounded by cold water, with attendant contact between arms 89 and 81, then the above described energizing circuit through coil 5| will be closed at the start of an oli-peak period when the timing device has moved contact arm 45 into engagement with contact arm 43. 'Ihis will, of course, result in heating of the water in the tank.

I may here point out that in case the amount of hot water in the tank at the start of an oipeak period was sufficient to envelope the tubular member 83 and to delay energization of the heater 61 and if withdrawal of hot water should occur during the delay period to such an amount as to envelope tubular member 83 in cold water, closure of the energizing circuit of coil 5| would occur as soon as contact arms 89 and 81 engaged each other, so that the heater 61 would be energized.

It is desired to cause energization of the coil 5| of the contactor at a predetermined later time after the start of an oli-peak period if all of the water in the tank'is not hot and for this purpose I provide an auxiliary camdisc 91 on shaft 3| adjacent to disc 33, which cam disc 91V is provided with a small ear or lug 99 of slightly larger radius than the main part of the periphery of disc 91. I provide means including a stop pin |0| which may be mounted on cam disc 33 to permit of adjusting disc 91 onV shaft 3| to any. desired position intermediate that 'shown in Fig. 2 of the drawing and that shown in Fig. 1 of the drawing. It is to be understood that whileI have shown a rather large peripheral extent of lug 99, this may be made relatively small since itk is necessary to make momentary contact only as will now be described, of an auxiliary control switch.

This auxiliary control switch |03 includes a relatively rigid contact arm |05'and a resilient contact arm |01 normally biased out of engagement with arm |05 so that a lug |09 of electric insulating material on` arm- |01 may rest on the periphery of cam disc 91. Contact arm 43 is connected through a conductor ||3 with conductor 93. If the quantity of hot water in the tank was such that tubular member 83 was surrounded by hot water and the switch-contacts 81 and 89 were out of engagement with each other at the start of an off-peak period, and if cam disc 91 was set on its shaft 3| so that lug 99 thereon would engage member |09 after two hours delay, the engagement of, contact arm |01 with contact arm |05 would cause closure of the following 'energizing circuit through coil 5|: From supply circuit conductor 31 through conductor 59, engaged contact arms 45 and 43, conductor engaged contact arms |05 and |01,

' conductor ||3, part of conductor 93, coil 5|, conductor 95, switch 1| and conductor 19 to the other supply circuit conductor 39. In other words, the cam disc 91 is effective to cause closure of the contactor and closure ofv they energizing circuit through the heater 61 at the time that contact arms, |05 and |01 are in engagement provided that the tank is not entirely full of hot water, that is, contact arm 13 is out of engagement with contact arm 69.

It is thus obvious that in case the quantity of hot water in the tank at the start of an off-peak period is more than a predetermined amount, energization of the heating element will be delayed an adjustably predetermined time after the start of an off-peak period, so long as there was an appreciable amount of cold water still in the tank, which amount of cold water would, of course, be located in the lower part of the tank.

It has hereinbefore been stated that the engagement between contact arms and |01 need be momentary only and the holding circuit for continuing the energization of the coil 5| will now be pointed out. Starting from'v supply circuit conductor 31 and extending through conductors 59 and 8|, through the contact members 55 and 51 of contactor 49, conductors 63, 65 and I through coil 5|, through conductor 95, contact arms 69 and 13 of thermal switch 1| and through conductor 19 to the other supply circuit conductor 39. It is evident that this holding circuit, once established, is not dependent upon either switch 4|` or |03.

Deenergization of the heater B1 will be effected when al1 oi the water in the tank has been heated to a predetermined temperature because of the action of the main thermally actuable switch 1| in causing disengagement of contact arm 13 from contact arm 69 with resultant opening of the circuit through the heater 61. If all of the water in the tank should happen to have been heated to a predetermined temperature during the off-peak period, the heater will be deenergized by reason of the opening of the switch 1! because of the movement of contact arm 13 out of engagement with contact arm 69. This will also interrupt the hereinbefore described holding circuit for coil 6| so that contactor 49 will also open. Should this condition of the tank being filled with hot water occur during an off-peak period and should withdrawal oi hot water occur during the rest of that olf-peak period, the heater will be again energized as hereinbefore set forth and should, for example, rapid withdrawals of hot water occur during the rest of the off-peak period with the result that all of the water in the tank`is not hot at the end of an oft-'peak period, the energization of heater 61 will be continued beyond the end of the oil-peak period and will actually continue until all of the water in the tank has been heated to a predetermined temperature when the hereinbefore described operation of the main thermal switch 1| will cause deenergization of the heater and it may be noted that it will thereafter be impossible to reenergize the heater until the start of the next following ofi'peak period.

I'he positions of certain parts of the timing device shown in Fig, 2 are those which will` cause starting of the energization of the heater 61 at the beginning oi an oiI-peak period irrespective of whether the auxiliary thermally actuable switch is subjected to hot water or to cold water. The user of my improved water heating system may thus easily and quickly meet unexpected operating conditions and start an on-peak part of the day with a desired quantity of hot water.

It may be noted that the system embodying my invention utilizes a single electromagnetic contactor in combination with-a main thermally actuable heater control switch, the two being connected in series circuit relation vrelatively to each other, to control the energization of an electric heater and energization of the heater may start with the start of an o-peak period under certain conditions as to the quantity of hot water in the tank at the start of the offpeak period, or the energization of the heater-may be delayed a predetermined adjustable time and if the heater is deenergized during the o-peak period because of the tank being full of hot water and withdrawals ol hot water occur during the rest of the oil-peak period, the heater will be again energized, which energlzation will continue beyond the end of the oil-peak period in case all of the water in the tank is not hot at the end of an oil-peak period. I may also point out that in case the tank contained enough hot water at the start of an oiI-peak period to delay energization of the heater and withdrawal of hot water occurred during vsuch delay period to an extent to subject thermally actuable switch ll to cold water, energization of coil 5| of contactor 49 would occur since contact arms 89 and 81 would move into engagement with each other under those conditions, with resultant engagement of contact bridging member 51 with iixed contact members 55. This would energize the electric heater 61.

While I have shown l"the auxiliary thermal switch subject to tank water temperature as being located substantially midway of the axial length of the tank, I do not desire to be limited thereto as it may be located in or on the tank at any other desired point, say at one-third or at two-thirds of the tank height and the amount of hot water in the upper part of the tank necessary to cause opening of this switch will vary substantially in accordance with the location of this switch. The cooperative positions of the electric heater and o! the lower thermal heater control switch are such that this thermal switch will not open until substantially all of the water in the tank is hot, that is, has been heated to a desired high temperature.

While I have illustrated and described a speciiic embodiment of water heating system embodying my invention, it is obvious that modications may be made therein and all such modiiications clearly coming within the scope of the appended claims shall be considered as being covered thereby.

I claim as my invention:

l. An oit-peak water heating system for a hot water tank comprising an electric heater, an electromagnetic switch for said heater, time and temperature responsive switches jointly controlling said electromagnetic switch to cause ener'- gization of said heater at the start of an oiI- peak period when the tank contains more than a predetermined quantity oi' cold water at the start of the oli-peak period, to delay for a iixed length of time after the start of an oil-peak period the energization of said heater when the tank contains less than said predetermined quantity ot cold water at the start of the offpeak period and to cause continuance of the energization of the electric heater beyond the oil-peak period in case the tank contains an appreciable quantity of cold water at the end of the oft-peak period, said energization continuing until substantially all of the water in the tank is hot.

2. An off-peak water heating system for a hot water tank comprising an electric heater, an electromagnetic switch tor said heater, a plurality of switches controlled respectively by time and by tank water temperature jointly controlling said electromagnetic switch to delay energization of said heater a iixed length of time after start of an oil-peak period in case less than a predetermined amount o! cold water is in the tank at the start of the o-peak period and during said delay, to cause energization ot Iwater tank comprising a single electric the heater during said delay time in case withdrawals of hot water from the tank cause it to contain more Vthan said predetermined amount of cold water, yto vcause prolongation of the energization of the heater beyond the end of the offpeak period in case more than a lesser predetermined amount of cold Water is in the tank at theend of the oli-peak period and to cause deenergization of the heater when substantially all of the water in the tank is hot.

3. An olf-peak water'heating System for a hot water tank comprising an electric heater, an electromagnetic switch for said heater, a plurality of switches controlled respectively by time and by tank water temperature jointly controlling said electromagneticvswitch to cause it to energize said heater Yat the start of an oit-peak period when the tank contains more than a predetermined quantity of cold water at the startV of an olf-peak period, to prolong the energization of the heaterbeyond the end of the off-peak period in case the tank contains an appreciable quantity of cold water at the end of the off-peak period, to deenergize the heater when all of the water in the tank is hot and to reenergize the heater after such deenergization in case withdrawals of hot waterv from the tank after such deenergization during the oil-peak period cause it to contain an appreciable quantity of cold water.

4. An oil-peak water heating system for a hot water tank comprising an electric heater, an

electromagnetic switch controlling said heater, f

a plurality of switches controlled respectively by time and by tank water temperature jointly controlling said electromagnetic switch to delay energization of said heater a xed length of rtime after start of an oil-peak period in case less than a predetermined amount of cold water is in the tank at the start of the olf-peak period, to cause heater energization during that time in case withdrawals of hot water from the tank causes the tank to contain more than said predeterminedamount of cold water, to cause deenergization of the heater at Yany time during the rest of the oil-peak period when all of the water in thetank is hot and to reenergize said heater at any time during the rest of the oli-peak period. after its deenergization in case withdrawals of hot Water from the tank cause the tank to contain an appreciable quantity of cold water. j;

5. An off-peak water heating system for a hot water tank comprising an electric heater, an electromagnetic switch for said heater, time and tank water temperature responsive switches jointlycontrolling the closure of said electromagnetic switch at a predetermined time of day when a predetermined amount of cold water is in the tank and a second tank Water temperature responsive switch for the electric heater effective to cause deenergization of said heater when substantially all of the water in the tank has been heated to a predetermined temperature.

6. An off-peak water heating system for a hot heater located adjacent to the bottom of the tank, an electromagnetic switch for said heater, a main thermally-actuable switch subject to the tank water temperature in series circuit relation with said electromagnetic switch for said heater and eiective to cause deenergization of said electric heater when substantially all of the' water in the tank has been heated to a predetermined f, temperature, an auxiliary thermally-actuable switch subject to the temperature of the water at an elevated part of the tank, a normally open switch in series circuit relation with said auxiliary thermally-actuable switch, a continuouslyoperative timer adapted to cause closure of said normally-open switch at thebeginning of an oilpeak period, said auxiliary thermally-actuable switch and said timer-controlled switch being jointly effective to cause closure of said electromagnetic switch and energization of said electric heater on closure of said timer-controlled switch and on presence of such an amount of cold water in the tank as to aiect said auxiliary thermallyactuable switch, said main thermally-actuable switch being effective to cause deenergization of the electric heater when substantially all of the water in the tank has been heated thereby to a given temperature.

7. An off-peak water heating system for a hot water tank comprising an electric heater, an

electromagnetic switch for said heater, a main' thermally-actuable,switch in series circuit relation with said electromagnetic switch for said heater and eiective to cause deenergization of said electric heater when substantially all of the water kin the tankhas been heated to a predetermined temperature, an auxiliary thermally-actuable switch subject to the temperature of the water atan elevated part of the tank, a normally-open switch in series circuit relation with said auxiliary thermallyactuable switch, a continuously operative timer adapted to cause closure of said normally-open switch at the beginning of an OIT-peak period, said auxiliary thermally-actuable switch and said timer-controlled switch being jointly effective to prevent closure of said electromagnetic switch and energization of said electric heater on closure of said timer-controlled switch and on presence of such an amount of hot water in the tank as to aiect said auxiliary thermallyactuable switch and a manually-adjustable second time-controlled switch jointly eiective with said rst named timer-controlled switch to' cause closure of said electromagnetic switch after an adjustably preset time interval after closure of said rst named timer-controlled switch.

8. An olf-peak water heating system for a hot water tank comprising an electric heater, an electromagnetic switch for said heater, time and tank Water temperature controlled switchesq jointly effective to cause closure of said electromagnetic switch and energization of said heater at a time after closure of the time-controlled switch varying with'the amount of hot water in the tank and thermally-actuable switching means for causing deenergization of said heater when all of the water in the tank is hot irrespective of the operative position of the time-controlled switch.

9. An off-peak water heating system for a' hot water tank comprising an electric heater, an electromagnetic heater control switch, a thermal heater control switch for deenergizing said heater when substantially all of the water in the tank is hot, a rst normally openswitch, a second thermal switch subject to tank water temperature, a second normally open switch, a continuously operative timer actuable to hold said first normally open switch in closed position during an off-peak period and to momentarily close said second normally open switch at a predetermined time during an off-peak period, electric connections between the coil of said electromagnetic switch, said second thermal switch and said iirst and second normally open switches to cause closing movementl of said electromagnetic switch and energization of said heater at the start of an oil-peak period in case less than a predetermined fractional part of the water content of the tank is hot and to delay causing closing movement of said electromagnetic switch and energization of the heater for a fixed time interval after the start of an oil-peak period in case more than said predetermined fractional part of the water content of the tank is hot.

10. An off-peak water heating system for a hot water tank comprising an electric heater, an electromagnetic heater control switch, a thermal heater control switch for deenergizing said heater when substantially all of the water in the tank is hot, a first normally open switch a second I thermal switch subject to tank water temperature, a second normally open switch, a continuously operative timer actuable to hold said iirst normally open switch in closed position during an off-peak period ad to momentarily close said second normally open switch at a predetermined time during an off-peak period, electric connections between said second thermal switch, said rst and second normally open switch and the coil of said electromagnetic switch to connect the coil, the second thermal switch and the iirst normally open switch in series circuit with each other and the second normally open switch in shunt circuit with said second thermal switch to preclude closing movement of said electromagnetic switch and energization of the heater at the start of an oit-peak period in case said second thermal switch is subject to hot water and to cause closing movement of the` electromagnetic switch and energization of the heater at the time of momentary closure of said second normally open switch.

l1. An off-peak water heating system for a hot water tankcomprising an electric heater, an electromagnetic heater control switch, a therma1 heater control switch for deenergizing said heater when substantially al1 of the water in the vtank is hot, a rst normally open switch, a second thermal switch' subject to tank water temperature, a second normally open switch, a continuously operative timer actuable to hold said ilrst normally open switch in closed position during an off-peak period and to momentarily close said second normally open switch at a predetermined time during an oil-peak period, electric connections between said second thermal switch, said rst and second normally open switch and the coil of said electromagnetic switch to connect the coil, the second thermal switch and the rst normally open switch in series circuit with each other and the second normally open switch in shunt circuit with said second thermal switch to preclude closing movement f said electromagnetic switch and energization of the heater at the start of an oil-peak period in case said second thermal switch is subject to hot 'water and to cause closing movement of the electromagnetic switch and energization of the heater at the time of momentary closure ofsaid second normally open switch said energization of the heater continuing until substantially all o! the water -in the tank is hot irrespective of the operative position of said rst normally open switch.

DANIEL J. MCCARI'HY. 

